.puzzle{
    width: 420px;
    height: 400px;
    margin: 20px auto;
}
.pieces{
    width: 98px;
    height: 98px;
    border: solid black 1px;
    background-color: #ab7947;
    float: left;
    font-size: 30px;
    line-height: 100px;
    text-align: center;
    color: white;
    -webkit-transition: 0.2s;/*浏览器前缀，兼容其他浏览器 chrome*/
    -moz-transition: 0.2s;/*firefox*/
    -ms-transition: 0.2s;/*ie*/
    -o-transition: 0.2s;/*opera*/
    transition: 0.2s;
}
.content{
    width: 420px;
    margin: 20px auto;
}